From Trading Idea to Executable System.

//+------------------------------------------------+
//| Session breakout, risk-based sizing            |
//+------------------------------------------------+
input double RiskPercent   = 0.5;   // risk per trade
input int    RangeStartHr  = 0;     // range window
input int    RangeEndHr    = 7;
input double MaxSpreadPts  = 18;

void OnTick()
{
   if(!IsNewBar() || SpreadPoints() > MaxSpreadPts) return;
   if(PositionsTotalFor(_Symbol, Magic) > 0)      return;

   Range r = SessionRange(RangeStartHr, RangeEndHr);
   if(!r.valid) return;

   double sl   = r.high - r.low;
   double lots = LotsForRisk(RiskPercent, sl);

   if(Close(1) > r.high) Buy(lots,  r.low,  r.high + 2*sl);
   if(Close(1) < r.low)  Sell(lots, r.high, r.low  - 2*sl);
}